In the semiconductor industry, tungsten thin films are usually deposited through use of a WF6 precursor and a H2 or SiH4 carrier gas. This process, however, is not able to form a WN thin film from a WF6 precursor and a NH3 reactant gas, because, when WF6 is used, there is always a fluorine contamination problem. This requires deposition of an extra barrier layer, such as TiN, to prevent direct contact of Si or SiO2 and WF6. See Yu et al., Critical Surface Reactions in the CVD of Tungsten by WF6 and WF6/SiH4 Mixtures, Materials Research Society, 1989, pp 221–230.